1. Technical Field
The embodiments herein generally relate to electrical filters, and, more particularly, to noise shaping active filters.
2. Description of the Related Art
Active filters are often realized using transconductance-C (gm-c) topologies or operational amplifier (opamp) based RC topologies. There are many ways to implement higher order filters using these two techniques; however, both techniques generally suffer from a limited noise performance. This is because the active and passive components in both gm-c and opamp-based active filter are in the signal path, which adds noise directly to the signal at all frequencies (i.e., no noise shaping is employed). Unfortunately, attempting to reduce the noise of such active filters to acceptable levels leads to prohibitively large power and area penalties.
Accordingly, the conventional filter solutions tend to suffer from the following: 1) higher noise that prevents such higher order filters from being used in low noise applications (such as a post-mixer amplifier in a wireless integrated receiver); 2) in many of these topologies increasing the filter order directly increases the noise; and 3) larger area and power consumption. Accordingly, there remains a need for a new noise shaping filter that reduces noise, power consumption, and accommodates a high dynamic range.